Today's digitally controlled or Digital Signal Processing (DSP) hearing instruments are often provided with a number of pre-set listening programs. These pre-set listening programs are often included to accommodate a comfortable and intelligible reproduced sound quality in differing listening environments. Audio signals obtained from these listening environments may have highly different characteristics, e.g. in terms of average and maximum sound pressure levels (SPLs) and/or frequency content. Therefore, for DSP based hearing prosthesis, each type of listening environment may require a particular setting of algorithm parameters of a signal processing algorithm of the hearing prosthesis to ensure that the user is provided with an optimum reproduced signal quality in all types of listening environments. Algorithm parameters that typically could be adjusted from one listening program to another include parameters related to broadband gain, corner frequencies or slopes of frequency-selective filter algorithms and parameters controlling e.g. knee-points and compression ratios of Automatic Gain Control (AGC) algorithms. Consequently, today's DSP based hearing aids are usually provided with a number of different pre-set listening programs, each tailored to a particular listening environment and/or particular user preferences. Characteristics of these pre-set listening programs are typically determined during an initial fitting session in a dispenser's office and programmed into the aid by transmitting or activating corresponding algorithms and algorithm parameters to a non-volatile memory area of the hearing prosthesis.
The hearing aid user is subsequently left with the task of manually selecting, typically by actuating a push-button on the hearing aid or a program button on a remote control, between the pre-set listening programs in accordance with the current listening or sound environment. Accordingly, when attending and leaving the multitude of sound environments in his/hers daily whereabouts, the hearing aid user may have to devote his attention to the delivered sound quality and continuously search for the best program setting in terms of comfortable sound quality and/or the best speech intelligibility.
In the past there have been made attempts to adapt signal processing characteristics of a hearing aid to the type of listening environment that the user is situated in. U.S. Pat. No. 5,687,241 discloses a multi-channel DSP based hearing instrument that utilises continuous determination or calculation of one or several percentile value of input signal amplitude distributions to discriminate between speech and noise input signals in the listening environment. Gain values in the frequency channels are subsequently altered in response to the detected levels of speech and noise.